1. Technical Field of the Invention
This disclosure relates to a computer system with a NAND flash memory for booting and storage.
2. Description of the Related Art
In a system such as a general PDA, a mobile phone, a set top box, or the like, ROM or NOR flash memory is mainly used for the system drive memory and NOR flash memory is used as the data storage memory. Flash memory is suitable for data storage because it has a volatility in which data can be written and erased and no refresh is needed. In particular, NOR flash memory is widely being used for booting and storage in systems that do not require a high speed interface.
With the growth of the system market, a memory capable of supporting high speed access, having large capacity, as well as being cost-effective due to service variety and high functionality has been requested. However, the conventional NOR flash memory does not fulfill such a request. Although conventional DRAM meets such a request at present, it is a volatile memory and is not suitable for data storage.
In the meantime, since the NAND flash memory is easy to realize, has a large capacity, and is cost-effective compared with the NOR flash memory, it is widely used as a large capacity memory. Also, since the NAND flash memory is easy to fabricate and has a good integrity, its use as a booting memory has been proposed.
In U.S. Pat. No. 5,535,357, issued to Moran et al., entitled “Flash memory system providing both BIOS and user storage capability”, an example of a flash memory used as a booting memory is disclosed. Referring to FIG. 1, in order to use a NAND flash memory as the booting memory, a flash controller 8 performs an interfacing between a NAND flash memory 4 and a system bus 2. Here, the NAND flash memory 4 has to store a separate emulation means. The emulation means is indicative of means for using a region of the NAND flash memory as the hard disk. The flash controller 8 intercepts the BIOS booting process and installs the emulation means in a system memory 3. In the construction of FIG. 1, the system booting is performed as follows.
First, a jump address for a BIOS region BS (located at block 1) is stored in a file system region FS (located at block 0) of a NAND flash memory 4. A memory mapping to the BIOS block BS is performed using a memory mapping circuit (or window circuit) arranged in the flash controller 8. With the memory mapping, an operating system region OS is moved to the system memory 3 to subsequently perform the system booting.
However, in order to use the NAND flash memory as the system booting memory by the aforementioned conventional method, the NAND flash memory 4 should be partitioned into the file system region FS, the BIOS region BS, the operating system region OS and the user data region UD as shown in FIG. 1. Also, the NAND flash memory 4 must have the emulation means which allows the NAND flash memory 4 to be recognized as the hard disk. In addition, the flash controller 8 must have the functionality to intercept the BIOS operating process and means for performing an address mapping to the BIOS region BS.
In the aforementioned conventional method, preparing to use the NAND flash memory and the flash controller as a booting memory and the necessary operational steps are complicated. Consequently, it is not easy to apply the conventional method to a general computer system.
Embodiments of the invention address these and other disadvantages of the conventional art.